초록 ▼

An equivalent to the spatial separation either side of a nominal median plane that is inherent in a bimorph (with one piezoelectric layer on one side, and the second on the other side of the plane) is attained by structurally shaping the cross-section of a simple, single piezoelectric layer (11) suc

An equivalent to the spatial separation either side of a nominal median plane that is inherent in a bimorph (with one piezoelectric layer on one side, and the second on the other side of the plane) is attained by structurally shaping the cross-section of a simple, single piezoelectric layer (11) such that it has a multiplicity of piezoelectric portions arranged in two generally-planar groups one either side of a median plane, so that any dimension change undergone by a portion on one side of that plane will tend to bend the whole device in the opposite direction to the same sense dimension change undergone by a portion on the other side of that plane. The simple, single layer acts as though it were a bimorph if elongate and beam-like, bending along its length, one end moving up/down, or back/forth, relative to the other but with any need for an internal, electrode.

대표청구항 ▼

The invention claimed is: 1. A piezoelectric device the body of which is a single layer of piezoelectric material shaped so as to have a multiplicity of separate, distinct piezoelectric portions disposed in two generally planar groups that extend along, one on each side of, a nominal median plane t

The invention claimed is: 1. A piezoelectric device the body of which is a single layer of piezoelectric material shaped so as to have a multiplicity of separate, distinct piezoelectric portions disposed in two generally planar groups that extend along, one on each side of, a nominal median plane through the whole body, which groups are thus spatially separated by and face each other across that median plane, with the result that any piezoelectric portion dimension change in the group on one side of the median plane will tend to bend the device normal to the median plane in the opposite direction to the same-sense piezoelectric portion dimension change in the group on the other side of that median plane, wherein the body is shaped as a ring, part ring or annulus, or as a disk, and the shape is corrugated such that the corrugations are straight across the body, and thus generally radial, or are at some angle to the theoretical radii, and are either straight or alternatively slightly curved into arcs. 2. A piezoelectric device that is a generally planar single-layer arcuate strip-like body having overall a broken annular shape, the body being physically shaped in a direction along its arcuate length so as to have corrugations extending across the strip, these corrugations forming separate, distinct piezoelectric-portion groups extending along and on each side of a nominal median plane through the whole body, which groups are thus spatially separated by and face each other across that median plane, with the result that any piezoelectric portion dimension change in the group on one side of the median plane will tend to bend the strip normal to the median plane across its length in the opposite direction to the same sense piezoelectric portion dimension change in the group on the other side of that median plane. 3. A device as claimed in claim 2, wherein the corrugations are disposed evenly and symmetrically about a centre line normal to the median plane. 4. A device as claimed in claim 2, wherein the median plane is co-planar with the device's neutral axis plane. 5. A device as claimed in claim 2, wherein the corrugations are not parallel and the pitch of the corrugations is relatively small compared to the smallest in-plane dimension of the device. 6. A multiplicity of devices as claimed in claim 2 formed into a stack. 7. A device as claimed in claim 1, wherein the corrugations are disposed evenly and symmetrically about a centre line normal to the median plane. 8. A device as claimed in claim 1, wherein the median plane is co-planar with a neutral axis plane of the device. 9. A device as claimed in claim 1, wherein the corrugations are not parallel and the pitch of the corrugations is relatively small compared to the smallest in-plane dimension of the device. 10. A multiplicity of devices as claimed in claim 1, formed into a stack. 11. A method of operating a piezoelectric device the body of which is a single layer of piezoelectric material shaped so as to have a multiplicity of separate, distinct piezoelectric portions disposed in two generally planar groups that extend along, one on each side of, a nominal median plane through the whole body, which groups are thus spatially separated by and face each other across that median plane, the method comprising activating the group of portions on one side of the median plane and the group of portions on the opposite side of the median plane to undergo a change in dimensions which is in an opposite sense for the two groups of portions, without clamping the device along the direction in which the portions extend, so that the piezoelectric device bends normal to the median plane along the direction in which the portions extend. 12. A method as claimed in claim 11, the overall shape of which is that of an elongate body shaped in a direction across the length of the elongate body so as to have said separate, distinct piezoelectric-portion groups extending along the body. 13. A method as claimed in claim 11, wherein the piezoelectric material is a ceramic material. 14. A method as claimed in claim 11, wherein the body of the single layer is a corrugated sheet. 15. A method as claimed in claim 14, wherein the corrugated sheet is generally planar. 16. A method as claim in claim 14, wherein the corrugated sheet is uniformly corrugated along its entire length. 17. A method as claimed in claim 14, wherein the shape of the corrugations is either sinusoidal or semicircular. 18. A method as claimed in claim 14, wherein the corrugations are reversed halfway along the body. 19. A method as claimed in claim 11, wherein the body is shaped as a ring, part ring or annulus, or as a disk, and the shape is corrugated such that the corrugations are straight across the body, and thus generally radial, or are at some angle to the theoretical radii, and are either straight or alternatively slightly curved into arcs.